This invention relates to a centrifugal governor for a fuel injection pump for use in an internal combustion engine such as a diesel engine, and more particularly to a centrifugal governor of this kind which has an improved function of increasing the quantity of fuel to be supplied to the engine at the start of same.
A centrifugal governor is known, e.g. from Japanese Patent Publication No. 58-7814, which comprises a control rack for regulating the quantity of fuel to be supplied to the engine, flyweights radially displaceable in response to the rotational speed of the engine, a tension lever pivotable through an angle dependent upon the amount of radial displacement of the flyweights, an idling spring for urging the tension lever against radially outward displacement of the flyweights, a torque cam pivotable about a fulcrum shaft thereof and having a cam surface including a cam surface portion determining a fuel increment to be applied at the start of the engine, a sensor lever having one end engaged by the control rack and another end disposed for engagement with the cam surface portion of the torque cam, the sensor lever being adapted to engage with the cam surface portion of the torque cam when the engine is in a starting condition, to permit displacement of the control rack into a fuel increasing position for starting the engine, a cancelling spring interposed between the torque cam and the tension lever and urging the torque cam with a force dependent upon the angularity of the tension lever to cause pivoting of the torque cam about the fulcrum shaft in a direction of disengaging the sensor lever from the cam surface portion of the torque cam, a control lever arranged to be operated at human will, and a floating lever interlocking with the control lever and having one end engaged by the control rack and another end operatively connected with the tension lever through a guide lever. In the centrifugal governor of this type, when the control lever is operated to a full speed position in order to start the engine, the floating lever is pivotally displaced about its end engaging the guide lever, to cause the control rack to be displaced to a starting fuel increasing position, while simultaneously pivotally displacing the tension lever to cause pivoting of the torque cam for control of the starting fuel quantity. However, due to resistance of the link members, the torque cam is pivoted after the control rack has been displaced, so that the sensor lever engaging the control rack can become engaged with the cam surface portion of the torque cam, to thus enable the control rack to be displaced into the starting fuel increment position.
However, when the accelerator pedal is stepped on to start the engine in cold weather, particularly at an ambient temperature of -20.degree. to -40.degree. C., the control rack does not move quickly toward the fuel increasing position in response to stepping-on of the accelerator pedal due to increased viscosity of lubricating oil etc. in such cold weather, causing slow motion of the sensor lever. As a result, the torque cam can be pivotally displaced to a position where the tip of the sensor lever cannot engage the cam surface portion of the torque cam, before the sensor lever becomes engaged with the torque cam, degrading the startability of the engine. Similarly, when the engine is started from a stopping position with the control rack returned to a fuel cut position by a stop lever or a fuel-cut lever, the sensor lever cannot easily engage the cam surface portion of the torque cam, also degrading the startability of the engine.